/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package studio.raptor.ddal.core.merger.aggregation;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.math.BigDecimal;
import java.util.List;

/**
 * 累加聚合单元.
 * 
 * @author jackcao
 * @since 3.0.0
 */
public final class AccumulationAggregationUnit implements AggregationUnit {

    private BigDecimal result;

    private static Logger LOG = LoggerFactory.getLogger(AccumulationAggregationUnit.class);

    public AccumulationAggregationUnit() {
    }


    @Override
    public void merge(final List<Comparable<?>> values) {
        if (null == values || null == values.get(0)) {
            return;
        }
        if (null == result) {
            result = new BigDecimal("0");
        }
        result = result.add(new BigDecimal(values.get(0).toString()));
        LOG.trace("Accumulation result: {}", result.toString());
    }
    
    @Override
    public Comparable<?>  getResult() {
        return result;
    }
}
